Transparent substrate and method of manufacturing the same

ABSTRACT

At least one monomolecule film is formed on a transparent substrate surface directly or via a protective film. The monomolecule film is formed with chemical coupling of chlorosilane surface active compound, for example, of the formula: 
     
       
         F(CF 2 )m(CH 2 )nSiR q X 3 — q   
       
     
     where m is an integer of from 1 to 15, n is an integer of from 0 to 15 provided that the total of m and n is an integer of from 10 to 30 and R is an alkyl or an alkoxyl group, or 
     
       
         F(CF 2 )m′(CH 2 )n′A(CH 2 )pSiR q X 3−q   
       
     
     where m represents an integer ranging from 1 to 8, n′ represents an integer ranging from 0 to 2, p represents an integer ranging from 5 to 25, q represents an integer ranging from 0 to 2, X represents a halogen atom or an alkoxyl group, R represents an alkyl or an alkoxyl group, and A represents —O—, a —COO— or —Si(CH 3 ) 2 —. The transparent substrate such as glass is made hydrophobic and free of contamination.

RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.09/570,264 filed May 12, 2000 (pending), which is a Continuation of U.S.patent application Ser. No. 08/383,428 filed Feb. 3, 1995 (abandoned)and U.S. patent application Ser. No. 08/279,686, filed Jul. 25, 1994,(abandoned). U.S. Pat. application Ser. No. 08/383,428 was a Divisionalof U.S. patent application Ser. No. 08/065,683 filed May 21, 1993(abandoned), and U.S. patent application Ser. No. 08/279,686 was aContinuation of U.S. patent application Ser. No. 08/065,683 (abandoned).U.S. patent application Ser. No. 08/065,683 (abandoned) was aContinuation of U.S. patent application Ser. No. 07/798,525, filed Nov.26, 1991 (abandoned). U.S. Pat. application Ser. No. 07/798,525 claimedpriority to two Japanese Applications, namely JP 2-405755 and JP3-038135.

FIELD OF THE INVENTION

This invention relates to a transparent substrate. More particularly,the present invention relates to a hydrophobic, oil-phobic and/orcontamination-free transparent substrate such as motor vehicle andbuilding window glasses, windshields, optical lenses and glass lensesetc.

BACKGROUND OF THE INVENTION

In order to prevent contamination of a transparent substrate such asglass, it has been proposed to make the surface of the transparentsubstrate as smooth as possible or coat the substrate surface with aprotective film such as a fluorine-based coating film or the like.Further, to prevent fogging of the transparent substrate surface, ahydrophilic polymer is coated thereon, or a heater is installed in oronto the transparent substrate.

Where the contamination of a transparent substrate stems from waterdrops, an antifogging effect can be obtained by installing a heater.However, the use of a heater has a drawback, namely a power source forthe heater is necessary. Furthermore, a heater which is buried in orinstalled on the surface of the transparent substrate may reduce thetransparency thereof. Coating the transparent substrate surface with ahydrophilic polymer or the like is comparatively simple. However, only atentative effect is achieved because the hydrophilic polymer may bepeeled off by rubbing the transparent substrate surface.

Where contamination of the substrate surface stems from other causes theabove methods are substantially meaningless. Accordingly, it has beenproposed to coat the transparent substrate surface with a protectivefilm, for example fluorine-based coatings. However, the adhesion betweenthe transparent substrate and a fluorine-based protective film is weak.Therefore the film is readily separated from the substrate surface. Inaddition, the fluorine-based protective film causes fogging of thetransparent substrate due to its opaqueness. Other protective filmmaterials can improve upon the transparency and adhesion of theflourine-based protective films. However, these materials do not enableeasily wiping-out of contaminants. Accordingly, it is a practical methodto make the surface of the transparent substrate as smooth as possible.However, there are limitations on the degree of smoothness of thesubstrate surface which one skilled in the art can attain. Thus, thereis a need for a contamination free, hydrophobic and/or oil phobictreated transparent substrate.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a highly hydrophobicand contamination free transparent substrate, which is free from theattachment of contaminants thereon or is capable of the ready removal ofany attached contaminants.

To attain this object, the instant invention provides a transparentsubstrate, which is provided on at least one surface thereon with achemically adsorbed monomolecule film containing a hydrophobic group.

A first aspect of this invention provides a transparent substratecomprising at least one monomolecule film formed as an outer mostsurface layer on at least one surface of a transparent substrate eitherdirectly or indirectly via a protective film. The monomolecule filmcontains a hydrophobic group and is bonded through covalent bonding tothe surface of the substrate or of the protective film. Preferably, theprotective film is itself one or more of such monomolecule filmscontaining a hydrophobic group and bonded through a covalent bond to thesurface of the substrate. A difference between the (a) monomolecule filmof the protective film and (b) the outer most surface layer monomoleculefilm is that (a) is at or near the end of the hydrophobic group and theprotective film monomolecule is bonded through a covalent bond to (b),the outer most surface layer monomolecule film. Another difference isthat (b) is bonded to the protective layer monomolecule film one layercloser to the outer most surface. One preferred embodiment of the firstaspect of this invention provides a transparent substrate comprising amonomolecule film formed as an outer surface layer on both surfaces of atransparent substrate either directly or indirectly via a protectivefilm. In particular, one of the surfaces (the first surface) is coveredwith a monomolecule film containing a hydrophobic group which iscovalently bonded to the first surface. The other surface (the secondsurface) is covered with a monomolecule film containing a hydrophilicgroup which is covalently bonded to the second surface.

According to another embodiment of the first aspect of this invention,the monomolecule film is formed by a covalent bond from a silanehalide-based or alkoxy silane-based surface-active compound of theformula:

F(CF₂)_(m)(CH₂)_(n)SiR_(q)X_(3-q)  (A)

where m represents an integer ranging from 1 to 15, n represents aninteger ranging from 0 to 15, the sum of m and n ranges from 10 to 30, qrepresents an integer ranging from 0 to 2, R represents an alkyl or analkoxyl group. and X is a halogen atom or an alkoxyl group; or

F(CF₂)_(m′)(CH₂)_(n′)A(CH₂)_(p)Si R_(q)X_(3-q)  (B)

where m′ represents an integer ranging from 1 to 8, n′ represents aninteger ranging from 0 to 2 p represents an integer ranging from 5 to25, q represents an integer ranging from 0 to 2, X represents a halogenatom or an alkoxyl group, R represents an alkyl or an alkoxyl group, andA represents —O—, a —COO— or —Si(CH₃)₂—.

A second aspect of this invention provides a method of modifying atransparent substrate, comprising:

applying, in a non-aqueous organic solvent, a silane based surfaceactive molecular compound having a reactive silane group at one end ofthe molecular compound and a hydrophobic group at the other end of themolecular compound to a surface of a transparent substrate or on asurface of a protective film provided on the transparent substrate. Themolecular compound is applied under conditions such that thesilane-based surface active compound is chemically adsorbed on thesurface thereby forming a monomolecule film on the transparentsubstrate. The film comprises a hydrophobic group, an —Si— group whereinthe film is covalently bonded to the applied surface.

One preferred embodiment of the second aspect of this invention providessuch a method which comprises:

contacting a surface of a molded transparent substrate with an organicsolvent solution of a silane-based surface active compound having areactive silane group at one end of the molecule and a hydrophobic groupat the other end of the molecule to form a chemically adsorbedmonomolecule film of the silane-based surface active compound on atleast one surface of the transparent substrate or over the entiresurface area.

Another preferred embodiment of the second aspect of this inventionprovides such a method which comprises:

contacting both of the surfaces of the molded transparent substrate witha non-aqueous solvent containing a material having at least twochlorosilyl groups;

washing the transparent substrate using a non-aqueous organic solutionto remove any non-reacted material having at least two chlorosilylgroups of the transparent substrate after the contacting step;

treating the transparent substrate with water after the non-reactedmaterial washing step, thereby forming a hydrophilic monomolecule filmcomposed of a silane material having at least one silanol group; and

treating the transparent substrate having the silanol group with asilane-based surface active compound having a reactive silane group atone end of the molecule and a hydrophobic group at the other end of themolecule, thereby laminating a chemically adsorbed hydrophobicmonomolecule film on the hydrophilic monomolecule film having silanolgroups.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the status of a glass surface in the formation of achemically adsorbed film;

FIG. 2 is a schematic sectional view enlarged in scale to the molecularlevel, showing the status of a glass surface in the formation of achemically adsorbed film;

FIG. 3 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the status of a glass surface in the formation of achemically adsorbed film;

FIG. 4 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the status of a glass surface in the formation of achemically adsorbed film;

FIG. 5 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the status of a glass surface in the formation of achemically adsorbed film;

FIG. 6 is a graph showing the surface tension or energy in variouschemically adsorbed films;

FIG. 7 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the surface of a windshield glass as an embodiment of thetransparent substrate according to the invention;

FIG. 8 is a schematic sectional view, enlarged in scale to the molecularlevel, showing the surface of a windshield glass as a differentembodiment of the transparent substrate according to the invention;

FIG. 9 is a schematic sectional view, enlarged in scale to the molecularlevel, showing a windshield glass as a further embodiment of thetransparent substrate according to the invention;

FIG. 10 is a schematic sectional view, enlarged in scale to themolecular level, showing the surface of a windshield glass as a furtherembodiment of the transparent substrate according to the invention; and

FIG. 11 is a schematic sectional view, enlarged in scale to themolecular level, showing the surface of a windshield glass as a furtherembodiment of the transparent substrate according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The transparent substrate component of the instant invention is usuallymade of transparent materials such as glass and plastic. Where thesubstrate is made of glass, its surface typically comprises hydrophilicmolecules such as hydroxyl groups. Where a plastic is the substratematerial, the surface may be readily made hydrophilic by an oxidizingtreatment. By contacting the substrate material with a non-aqueousorganic solvent solution of a compound having a carbon chain and areactive silane group at one end, a reaction between active hydrogens inthe hydrophilic groups of the substrate surface and the reactive silanegroup forms a monomolecule film. The monomolecule film is bonded to thesurface by an —SiO— group containing chemical bond (i.e., a covalentlybonded). Such a reaction is called a chemical adsorption reaction, andthe monomolecule film obtained by this reaction is called a chemicallyadsorbed single molecule (or unimolecule or monomolecule) film. In use,when the chemically adsorbed monomolecule film is covalently bonded to areal image side mirror surface, its adhesion is so strong that usuallyit is not separated unless the surface of the transparent substrate iscut away. Furthermore, because the compound has a hydrophobic group atthe other end, the hydrophobic properties of the monomolecule provides acontamination free effect.

As noted before, the transparent substrate material may be a plasticmaterial. Suitable plastic materials include acrylic resins andpolycarbonate resins. Such plastic substrates may be used in addition toglass, although glass is most extensively used.

The surface of the transparent substrate has an exposed hydrophilicgroup. Examples of hydrophilic groups are those groups having activehydrogen, e.g., hydroxyl groups, carbonyl groups, amino groups, iminogroups, etc. Where the transparent substrate surface does not have asufficient amount of hydrophilic groups, the surface is renderedhydrophilic by usual means such as electron or ion beam irradiation inan oxygen or nitrogen atmosphere.

The molecule constituting the chemically adsorbed monomolecule film maybe a silane-based surface active compound having a chlorosilane(—SiCl_(v)Y_(3-v)) group or an alkoxysilane (Si(OW)_(v)Y_(3-v)) group atone end of the molecule and a hydrocarbon group or fluorine-substitutedcarbon at the other end of the molecule. In the above formulas, vrepresents an integer ranging from 1 to 3, Y represents a hydrogen atomor a lower alkyl (for example C₁ to C₆) or lower alkoxyl group (forexample C₁ to C₆), and W represents a lower alkyl group. Among thesilane-based surface active compounds mentioned above,chlorosilane-based surface active compounds are preferred because theycan reliably undergo a chemical adsorption reaction to form a chemicallyadsorbed monomolecule film at room temperature. Among thechlorosilane-based surface active compounds, those having atrichlorosilane group (v is 3) are preferred because siloxane bondsintervene between adjacent adsorbed molecules. Further, in order toincrease the concentration of the adsorbed molecule, the silane-basedsurface active compound having a straight chain is preferred. Examplesof especially preferred chlolosilane-based surface active compounds arethose represented by the formulas:

R¹—SiCl_(v)Y_(3-v)  (C) and

CF₃—(CF₂)_(t)—(R²)_(r)—SiCl_(v)Y_(3-v)  (D)

where t is an integer of at least 0, preferably 0 to 10, r is 0 or 1, R¹is an alkyl group of at least 6 (preferably 8 to 22) carbon atoms whichmay contain a vinyl (CH₂=CH—) or ethynyl (CH≡C—) group or may beinterrupted by a COO group or by a silicon or oxygen atom, R² is analkylene group of at least one (preferably 1 to 20) carbon atoms whichmay contain a vinylene (—CH=CH—), ethynylene (—C≡C—) group or may beinterrupted by a COO group or by a silicon or oxygen atom, and Y is ahydrogen atom, a lower alkyl group (for example C₁ to C₆) or loweralkoxyl group (for example C₁ to C₆), and v is an integer ranging from 1to 3. Preferably, those chlorosilane-based surface active compounds have12 to 22 carbon atoms. More specific examples include:

CH₃(CH₂)₉SiCl₃,

CH₃(CH₂)₁₅SiCl₃,

CH₃CH₂O(CH₂)₁₅SiCl₃,

CH₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃,

CF₃(CF₂)₇(CH₂)₂SiCl₃,

CF₃CH₂O(CH₂)₁₅SiCl₃,

CF₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃,

CF₃(CF₂)₃(CH₂)₂Si(CH₃)₂(CH₂)₉SiCl₃,

CF₃COO(CH₂)₁₅SiCl₃,

CF₃(CF₂)₅(CH₂)₂SiCl₃.

Those surface active compounds in which R¹ in the above formulascontains a vinyl or ethynyl group are preferred, because apolymerization of unsaturated bonds with a catalyst, with light or highenergy irradiation, may occur. Polymerization of unsaturated bondsresults in intramolecular bonds and therefore an undesirably firmermonomolecule film.

Furthermore, the chlorosilane-based surface active compounds having ahydrophobic group containing a fluoro-carbon group are particularlypreferred, because the resulting monomolecule film is highly hydrophobicas well as an oil-phobic effect (i.e., oil-repellant).

The transparent substrate according to the instant invention is usuallymanufactured from a molded transparent substrate.

When the chlorosilane-based surface active material is used, thechemically adsorbed monomolecule film usually has to be washed withoutcontact with water. Water should be avoided because any of the remainingunreacted chlorosilane-based surface active compound reacts with thewater component of the wash and becomes whitish in color.

Further, the clorosilane-based surface active compound has to bedissolved in a non-aqueous (substantially non-water) organic solventbecause it is highly reactive with water. Examples of applicablesolvents include n-hexadecane, toluene, xylene, dicyclohexyl, carbontetrachioride, chloroform, or freon 113. These solvents may be usedeither alone or in combination. However, it is possible to use methylalcohol or ethyl alcohol as the solvent in cases when other silane-basedsurface active compounds are used rather than those based onchlorosilane.

To form the chemically adsorbed monomolecule film according to theinvention, one surface of the transparent substrate may be contactedwith a material having at least two chlorosilyl groups, before asilane-based surface active compound containing a hydrophobic group ischemically adsorbed on the transparent substrate surface. The materialhaving at least two Cl—Si groups reacts with an activehydrogen-containing group of the transparent substrate surface, reactingone or more Cl—Si groups but not all of them, so the unreacted Cl—Sigroups remain in the reacted material. The surface of the transparentsubstrate thus-treated is then washed with an organic solution to removethe unreacted material containing at least two chlorosilyl groups. Thesurface is then treated with water (washing with water or exposing toair to react with moisture in the air) to form a monomolecule filmcontaining silanol groups (Si—OH) on the surface of the substrate (seeFIG. 9).

Formation of a monomolecule film containing silanol groups is desirablebecause a silane-based surface active compound can be chemicallyadsorbed at a high concentration even when the substrate has only a verysmall quantity of hydrophilic groups, such as a quartz glass or temperedglass. Examples of materials having at least two chlosilyl groups are:

Si Cl₄, SiHC1 ₃, SiH₂Cl₂,

Cl—(SiCl₂O)_(i)SiCl₃, and

H₁(R³)_(3-l)Si(R⁴)_(i)SiCl_(k)(R⁵)_(3-k).

It is usually desired that the number of Cl—Si bonds is as large aspossible for high concentration chemical adsorption of the silane-basedsurface active compound containing hydrophobic groups. In the aboveformulas, i represents an integer such as 1 to 4, 1 and k each representan integer ranging from 1 to 3, R³ and R⁵ are lower-alkyl groups, and R⁴represents an alkylene group with a carbon number of at least 1 such as1 to 6. Preferably the materials have 3 or 4 Cl—Si bonds and areinorganic. Therefore, SiCl₄ is most preferred as the material containinga chlorosilyl group, because it is a very small molecule and is highlyreactive for producing silanol groups. Thus it is highly effective formaking a quartz glass surface uniformly hydrophilic.

It is possible to form a chemically adsorbed mono-molecule filmcontaining a hydrophobic group on only one surface of a transparentsubstrate and form a chemically adsorbed monomolecule film containing ahydrophilic group on the other surface, thus obtaining a substrate withhas different characteristics on opposite sides. Such a substrate may beobtained by chemically adsorbing the above-mentioned material containinga chlorosilane group on both surfaces of a transparent substrate. Bothsurfaces are then treated as described above to form silanol groups. Thesurface on which it is desired to leave a hydrophilic monomolecule filmis then coated with an aqueous solution of a water-soluble polymermaterial, e.g., polyvinyl alcohol or Pullulan. (Pullulan is a trademarkof Hayashibara Shoji Kabusiki Kaisha, and is a white powdery substanceformed by hydrolyzing Pullulanase into more than 94% maltotriose). Achemically adsorbed monomolecule film containing a hydrophobic group isthen formed on the other surface of the substrate. Subsequently thewater-soluble polymer material is washed away with water.

The chemically adsorbed monomolecule film according to the invention maybe either a single monomolecule layer or a lamination of two or moremonomolecule layers. In the latter case, however, it is necessary toform chemical bonds between adjacent laminated layers. For producingsuch a lamination of monomolecule layers, one preferred method is asfollows. First a chlorosilane based surface active compound (forexample, of the formula (C) mentioned above) having a group (such as avinyl or ethynyl group) that can subsequently be converted to an activehydrogen-containing reactive group (such as a hydroxyl, imino or aminogroup) is used to form a monomolecule film. The convertible group isthen converted to the active hydrogen-containing reactive group. Achlorosilane-based surface active compound is applied to this treatedsurface to form a hydrophobic monomolecule film.

The chemically adsorbed monomolecule film formed on the substratesurface is as thin as of the order of the nanometer (nm) and does notspoil the intrinsic transparency of the substrate. In addition, thechemically adsorbed monomolecule film according to the invention hashydrophobic properties and is therefore not readily susceptible tosurface contamination. Further, by forming a chemically adsorbedhydrophobic monomolecule film on one surface of a transparent substrateand forming a chemically adsorbed hydrophilic monomolecule film on theother surface of the substrate, a transparent substrate which hashydrophobic and contamination-free effects on one surface and anantifogging effect on the other surface can be obtained.

This invention can be applied to a variety of materials including adisplay-form touch panel switch, a face plate for photocopy machine, afresnel plate for an overhead projector, a display glass, a displayoptical filter, a halogen lamp, a mercury lamp a sodium lamp, anelectric bulb, a chandelier, a glass or plastic lens, a microscope lensa telescope lens, a binocular lens, a magnifying glass lens and otherapparatus lenses.

This invention will now be illustrated with reference to the followingexamples and the drawings, but the scope of the invention is not to beconstrued as limited to these examples.

EXAMPLE 1

In a chloroform solution containing 80 wt % n-hexadecane and 12 wt %carbon tetrachloride a silane-based surface active compound representedby a formula:

CH₂=CH—(CH₂)₁₆—SiCl₃

containing vinyl groups (CH₂=CH—)₂ (see FIG. 1) is dissolved to aconcentration of 3×10⁻³ to 5×10⁻² Mol. A glass substrate 1 as atransparent substrate was dipped into the solution and held at roomtemperature for one hour. The surface of the glass substrate 1 containeda number of hydroxyl groups and a reaction took place between thechlorosilyl groups (—SiCl) in the chlorosilane-based surface activecompound and the hydroxyl groups (—OH) and a bond represented such asformula 1:

is formed on the substrate surface.

The glass substrate 1 was then washed with freon 113 to remove thematerial remaining on the surface without any reaction, followed bywashing the surface with water or exposing the surface to air to reactwith moisture in the air. The —SiCl group was changed to a —SiOH groupas in formula 2.

Each silanol group (—SiOH) was then dehydrated and crosslinked to form asiloxan bond (—Si O—) as in formula 3.

Thus, an adsorbed monomolecule protective film 3 containing a vinylgroup 2 was formed as a single layer with a thickness from about 2 to 3nm on the surface in a chemically coupled form via oxygen atoms (seeFIG. 1). The glass substrate is then irradiated in an atmospherecontaining oxygen or N₂ (or in air) with about 3 Mrads of an energy beam(e.g., electron beam, X-rays, gamma (γ) rays, ultraviolet (UV) rays orion beam), thus providing the vinyl group portion 2 with a hydroxyl(—OH) groups 4 (in case of oxygen atmosphere) as shown in FIG. 2 oramino (—NH₂) group 5 (in case of nitrogen atmosphere) as shown in FIG.3. The hydroxyl, amino, and/or imino groups may be formed in air.

The fact that these functional groups are attached to vinyl groups isconfirmed from FT-IR analysis.

It is possible to process the vinyl groups arranged on the surface inplasma containing O₂ or N₂ as well to form an adsorbed monomoleculeprotective film 3-1 (see FIG. 4) with attached —OH groups as shown inFIG. 2 or an adsorbed monomolecule protective film 3-2 with attached—NH₂ groups as shown in FIG. 3.

Finally, a solution of a mixed solvent composed of 80 wt % n-hexane, 12wt % carbon tetrachloride and 8 wt % chloroform was prepared bydissolving a silane-based surface active compound containing fluorinerepresented by a formula:

F(CF₂)_(m)(CH₂)_(n)SiR_(q)X_(3-q)  (A)

where m represents an integer ranging from 1 to 15, n represents aninteger ranging from 0 to 15, the sum of m and n ranges from 10 to 30, qrepresents an integer ranging from 0 to 2, R represents an alkyl or analkoxyl group, and X is a halogen atom or an alkoxyl group; or

F(CF₂)_(m′)(CH₂)_(n′)A(CH₂)_(p)SiR_(q)X_(3-q)  (B)

where m′ represents an integer ranging from 1 to 8, n′ represents aninteger ranging from 0 to 2, p represents an integer ranging from 5 to25, q represents an integer ranging from 0 to 2, X represents a halogenatom or an alkoxyl group, R represents an alkyl or an alkoxyl group, andA represents —O—, a —COO— or —Si(CH₃)₂ , for instance:

CF₃CH₂O(CH₂)₁₅SiCl₃

in a concentration of the order of 2×10⁻³ to 5×10⁻² Mol. The glasssubstrate with the adsorbed monomolecule protective film 3-1 or 3-2formed thereon was dipped in to the solution and held therein for onehour. The —OH group, —NH group or —NH₂ group were exposed on thesubstrate surface as shown in FIG. 2 or 3, a reaction was brought aboutbetween the chlorosilyl group of the chlorosilane-based surface activecompound containing fluorine and the —OH, —NH or —NH₂ groups. Thuscovalent bonds were formed on the surface, represented as the followingformula 4.

This reaction proceeds substantially the same as above in formulas 1 to3.

Thus, a highly concentrated monomolecule film lamination 7 is formed onthe surface of the glass substrate such that an adsorbed monomoleculefilm 6 containing fluorine is chemically bonded to a lower is adsorbedmonomolecule film 3-1 as shown in FIG. 4 or to a lower adsorbedmonomolecule film 3-2 as shown in FIG. 5.

Where no monomolecule film is required between a hydrophobic oil-phobicsurface film and a glass substrate, a chlorosilane-based surface activecompound may be used to form an adsorbed monomolecule protective film.By so doing, a single layer of adsorbed monomolecule protective filmcontaining fluorine on the surface can be formed.

Where a plurality of monomolecule films are necessary as protectivefilms, CH₂═CH—(CH₂)_(n)SiCl₃ may be used as a chemical adsorptionreagent. The steps of chemical adsorption and radiation irradiation maybe repeated, and finally a chlorosilane-based surface active compoundcontaining fluorine may be adsorbed as a chemical reagent. Thus, ahydrophobic oil-phobic film comprising a single layer of an adsorbedmonomolecule film containing fluorine may be formed on the surface via aplurality of necessary protective films.

In the above embodiment, CF₃CH₂O(CH₂)₁₅SiCl₃, was used as a silane-basedsurface active compound containing fluorine outer most surface. However,it is possible to use other compounds as well, for instance;

CF₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃,

CF₃(CF₂)₃(CH₂)₂Si(CH₃)₂(CH2)₉SiCl₃,

CF₃COO(CH₂)₁₅SiCl₃, and

CF₃(CF₂)₇(CH₂)₂SiCl₃.

The surface energy or tension in the adsorbed monomolecule film wasmeasured by evaluation of the water dip angle of contact (with anautomatic contact angle gauge manufactured by Kyowa Kaimen Kagaku Co.).The results are shown in FIG. 6. FIG. 6 is a graph showing relationsbetween cos θ and surface tension.

As is seen from FIG. 6, the surface energy is reduced as the number offluorine atom increases. It is confirmed that when the number offluorine atoms is 9 or more, the surface tension of the film is lowerthan that of polytetrafluoroethylene and that the surface is very highlyhydrophobic and oil-phobic.

The water wetting angle measured at the surfaces of the adsorbed filmwas found to be about 140 to 150 degrees.

Thus, by using such glasses, it is possible to provide a wiperless motorvehicle windshield or windscreen glasses and simultaneously preventfogging of the glass lens surface.

In FIG. 6, F17, F9, F3 and NTS designate adsorbed monomolecular filmsrespectively of;

CF₃(CF₂)₇(CH₂)₂—Si(CH₃)₂(CH₂)₉SiCl₃,  F17;

CF₃(CF₂)₃(CH₂)₂O(CH₂)₁₅SiCl₃,  F9;

CF₃COO(CH₂)₁₅SiCl₃, and  F3;

 CH₃(CH₂)₁₉SiCl₃  NTS;

The above embodiment is directed to tempered glass. However, the instantinvention is applicable to all the glasses where improvement of thequality of the glass surfaces is a goal. For example, the abovedescribed embodiment finds particular use as a film for window glassesin vehicles, electric cars, aircraft and other means of transport, aswell as mirrors, glass vessels, glass or plastic lenses and other glassor plastic surfaces wherein hydrophobic and oil-phobic characteristicsare required.

Further, while the above embodiment is concerned with the adsorbedmonomolecule films as glass protective films, the transparent substrateaccording to the invention is by no means limited to glass, but it mayof course be protective films having functions as light-blocking films,ultraviolet absorption films and infrared absorption films as well.

Further, the glass is not limited to colorless transparent glass, butthe invention is applicable to roughened surfaces and also to coloredglass and glass fibers.

In general, the invention is applicable to all techniques of chemicalcoupling of glass or plastic having hydrophilic groups on the surfaceand a silane-based surface active compound containing a fluorophobic byusing a chemical adsorption process.

Where the surface of the protective film or transparent substrate itselfis not hydrophilic, the silane-based surface active compound containinga hydrophobic group may be provided after making the surface hydrophilicby usual methods, such as corona discharge in an atmosphere containingoxygen or alternatively by spattering.

The chlorosilane-based surface active compounds, in one preferredembodiment, are represented by the formulae

F(CF₂)_(m)(CH₂)_(n)SiR_(q)X_(3−q) or

F(CF₂)_(m′)(CH₂)_(n′)A(CH₂)pSiR_(q)X₃₋q

When one of these compounds is employed, a highly concentrated and verythin organic film can be formed. The film is substantially pin holefree, with a uniform thickness, thereby forming a hydrophobic oil-phobicmonomolecule film chemically coupled to the glass substrate surface. Thesymbols in the above formulas (A) and (B) are as defined hereinbefore.

It is thus possible to effect a very highly durable surface treatmentfor prevention of contamination, fogging and wetting of the glasssurface.

EXAMPLE 2

A transparent substrate, shaped for use as a motor vehicle windshield orwindscreen glass, was washed with an organic solution. Simultaneously amaterial containing a fluorocarbon group and a chlorosilane group havingthe formula:

 CF₃(CF₂)₇(CH₂)₂SiCl₃

was dissolved in a non-aqueous solvent, i.e., a mixed solvent composedof 80 wt % of n-hexadecane, 12 wt % of carbon tetrachloride and 2-8 wt %of chloroform. The windshield glass was dipped into the solution andimmersed for about 2 hours. The windshield glass had numerous hydroxylgroups on the surface, and thus a dehydrochlorination reaction wasbrought about between the chlorine in chlorosilyl (—SiCl) group of thematerial containing a fluorocarbon group and a chlorosilane group and ahydroxyl group and covalent bonds represented by formula 5 below wereformed over the entire surface of the windshield glass. This reactionproceeded substantially the same as described above in formulas 1 to 3.

Thus, a single layer of chemically adsorbed monomolecule film 12containing fluorine was formed in a state chemically coupled to thewindshield glass 11 by siloxane bonds, as shown in FIG. 7. The thicknessof this chemically adsorbed monomolecule film was assumed from themolecular structure to be about 1.5 nm. The monomolecule film waschemically coupled very firmly.

The treated windshield glass was then tested to compare the propertiesof treated windshield glass with untreated windshield glass. The treatedwindshield glass had greatly reduced contamination compared towindshield glass without the above-described treatment. Contaminants, ifattached, could be easily removed by merely rubbing the glass with abrush or the like. Doing so produced neither scars nor scratches on thesurface of the windshield glass 11. Further, it was possible to removeoily contaminants by merely washing with water.

Where plastic materials such as polyacrylic resins and polycarbonateresins were used as the material of the transparent substrate, thetechniques described above could be used to oxidize the surface.Subsequently, the oxidized surface could then be treated with water orair, as also described above, to make the surface hydrophilic. Inparticular, this means plasma treatment of the surface at 300 W forabout 10 minutes to make the surface oxidized and hydrophilic whilereplacing the adsorption liquid with a freon 113.

EXAMPLE 3

A solution was developed by dissolving about 1 wt. % of SiCl₄ as amaterial containing chlorosilyl groups in a chloroform solvent as anon-aqueous solvent. A windshield glass with the surface containing lesshydroxyl groups (although hydrophilic, e.g., an annealedly temperedglass) was dipped into the solution and immersed for about 30 minutes.Then a dehydrochlorinizing reaction was brought about on the surface ofthe windshield glass 21 due to the presence of some hydroxyl (—OH)groups 2 as hydrophilic groups on the surface, as shown in FIG. 8. Achlorosilane monomolecule film constituted by a material containingchlorosilyl groups was formed. By using SiCl₄ as a material containingchlorosilyl groups, a dehydrochlorination reaction was brought about onthe surface of the windshield glass 21 even in the presence of only asmall amount of hydrophilic OH groups 22 on the surface of the frontwindow glass 21. Furthermore, molecules such as formula 6 and 7 aresecured to the surface via —SiO— bonds.

In this case, non-reacted SiCl₄ may also be present on the chlorosilanemonomolecule film. However, by subsequently washing the surface of thewindshield glass 21 with chloroform as a non-aqueous solvent and thenwith water, the hydroxyl groups and non-reacted SiCl₄ molecules on thesurface can be removed to obtain on the surface a siloxane monomoleculefilm 23. The film is represented as formula 8 and 9 as shown in FIG. 5.

The monomolecule film 23 formed in this case is completely coupled tothe surface of the windshield glass 21 via chemical bonds of —SiO—, andtherefore it is never separated from the surface. In addition, thesiloxane monomolecule film 23 thus obtained has numerous surface —SiOHbonds, the amount of which roughly corresponds to about three times thenumber of the initial hydroxyl groups.

In the solution mentioned before in connection with Example 2, thewindshield glass was dipped in to the solution and immersed for aboutone hour. Thereupon, the windshield glass 21 developed the siloxanemonomolecule film 23 on its surface. As a result, bonds as shown such asabove in formula 5 were formed on the surface of the siloxanemonomolecule film 23.

Thus, a chemically adsorbed monomolecule film 24 containing fluorine wasformed to a thickness of about 1.5 nm. over the entire glass surface ina state chemically coupled to the lower siloxane monomolecule film 23,as shown in FIG. 10. A separation test showed that the monomoleculefilms are never separated.

The windshield glass of this example was tested under real useconditions. The results indicate that no water drops were attached dueto the hydrophobic effect of the surface fluorine. Acetone containingwax was blown against the glass by assuming the flow of wax component.It was found that oil was repelled and no fogging was produced due tothe effect of the oil-phobic properties of fluorine in the monomoleculefilm chemically adsorbed to the surface. In addition, contaminants thatwere attached could be easily wiped away.

EXAMPLE 4

A transparent substrate, a display-form touch panel glass (switch of CRTglass), was prepared and washed with an organic solvent.Simultaneously,, a material containing carbon fluoride groups andchlorosilane groups, namely

CF₃(CF₂)₇(CH₂)₂SiCl₃

was dissolved to a concentration of 1 wt. % in a non-aqueous solvent,i.e., a mixed solvent containing 80 wt. % of n-hexadecane, 12 wt. % ofcarbon tetrachloride and 8 wt. % of chloroform. The CRT glass was dippedinto the solution and immersed for about 2 hours. The CRT glass hadnumerous hydroxyl groups on the surface, and thus a dehydrochlorinationreaction was brought about between the chlorine in —SiCl groups of thematerial containing carbon fluoride groups and chlorosilane groups andhydroxyl groups on the surface. This reaction produced bonds representedby above formula 5 below over the entire surface of the CRT glass. Thisreaction proceed substantially the same as above in formulas 1 to 3.

Thus, a single layer of chemically adsorbed monomolecule film containingfluorine was formed and chemically coupled (i.e., covalently bonded) tothe CRT glass by siloxane bonds. The thickness of this chemicallyadsorbed monomolecule film was about 1.5 nm. The monomolecule film waschemically coupled very firmly and was never separated.

The resultant CRT glass was tested under actual use conditions. Itscontamination affinity was found to be greatly reduced compared to CRTglass without treatment. Contaminants, if attached, could be easilyremoved by merely wiping the glass with a paper or the like. Doing soproduced neither scars nor scratches on the surface of the CRT glass.

EXAMPLE 5

This example is directed to a fresnel plate glass for an overheadprojector wherein the surface contains less hydroxyl groups, althoughstill hydrophilic in nature, e.g., an annealedly tempered glass. Theglass was treated by immersing the glass for about 30 minutes in asolution. The immersion solution was developed by dissolving about 1 wt.% of SiCl₄ as a material containing chlorosilyl groups in a chloroformsolvent (a non-aqueous solvent). The immersion initiated a chemicaldehydrochlorinizing reaction on the surface of the fresnel plate glassdue to the presence of some hydroxyl (—OH) groups as hydrophilic groups(inner layer film) on the surface. As the inner layer film formingmaterial, other materials could be used in place of SiCl₄ such asSiHCl₃, SiH₂Cl₂, Cl—(SiCl₂ O)n SiCl₃ (n being integer).

A chlorosilane monomolecule film (inner layer) constituted by a materialcontaining chlorosilyl groups was formed on the glass. By using SiCl₄ asa material containing chlorosilyl groups, a dehydrochlorination reactionwas brought about on the surface of the fresnel plate glass even in apresence of only a small amount of hydrophilic OH groups on the surfaceof the fresnel plate glass. Furthermore, molecules described above byformulas 6 and 7 were secured to the surface via —SiO— bonds.

In this case, non-reacted SiCl₄ is also present on the chlorosilanemonomolecule film. By subsequently washing the surface of the fresnelplate glass with chloroform (as a non-aqueous solution) and then washingwith water, the hydroxyl groups and non-reacted SiCl₄ molecules on thesurface can be removed. The removal of the hydroxyl groups andnon-reacted SiCl₄ results in a siloxane monomolecule film representedsuch as above formulas 8 and 9 on the surface.

Further, as a material containing carbon fluoride groups andchlorosilane groups;

CF₃(CF₂ )₇(CH₂)₂SiCl₃

was dissolved to a concentration of 2 wt. % in a non-aqueous solvent,i.e., a mixed solvent containing 80 wt. % of n-hexadecane, 12 wt. % ofcarbon tetrachloride and 8 wt. % of chloroform. The glass was immersedinto the solution for about 1 hour. The glass had numerous hydroxylgroups on the surface, and thus a dehydrochlorination reaction wasbrought about between (1) the chlorine in the —SiCl groups of thematerial containing carbon fluoride groups and chlorosilane groups and(2) hydroxyl groups. The reaction produced bonds represented by aboveformula 5 over the entire surface of the glass.

Thus, the chemically adsorbed monomolecule film containing fluorine wasformed in a state chemically coupled to the glass by siloxane bonds. Thethickness of this chemically adsorbed monomolecule film was assumed fromthe molecular structure to be about 1.5 nm. The monomolecule film waschemically coupled very firmly and was never separated.

When chemically adsorbing a monomolecule film using a non-aqueoussolvent incorporating carbon fluoride groups and chlorosilane groups, anaqueous solution containing polyvinyl alcohol was also coated as ahydrophilic film. The hydrophilic film has resistance against an organicsolvent on the surface which was desired to be left hydrophilic (inorder to impart an antifogging effect). After the adsorption was over,the hydrophilic film was washed with water, thus obtaining a windshieldglass with a hydrophobic, oil-phobic contamination free monomoleculefilm 24 formed on one surface and a monomolecule film 23 containinghydrophilic hydroxyl groups on the other surface, as shown in FIG. 11.The antifogging effect of this glass was tested under simulated actualuse conditions, and it was found that the glass surface left hydrophilicwas never fogged.

In Example 2, only a single layer of monomolecule film was formed, andin Example 3 only a single layer of silane-based surface active compoundcontaining fluorine was formed after formation of a single layer ofsiloxane monomolecule film. However, the same effects can be obtained bylaminating a plurality of chemically adsorbed monomolecule filmsaccording to the invention instead of forming only a single layer.

Further, while the above example used CF₃(C F₂)₇(CH₂)₂SiCl₃ by adding orincorporating vinylene (—CH═CH—) or ethynylene (—C≡C—) groups to or inportion represented as R in chlorosilane-based surface active compoundrepresented as CF₃(CF₂)_(t)—(R²)y—SiCl_(v)X_(3-V), (wherein the symbolsare as defined before) crosslinking can be obtained with about 5 Mradsof electron beam radiation after the formation of the monomolecule filmfor further improvement of the hardness of the monomolecule film.

Alternative compounds could be used in addition to or in place of theabove described trichlorosilane-based surface active compounds. Forexample:

 CF₃CH₂O(CH₂)₁₅SiCl₃,

CF₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃,

CF₃(CF₂)₃(CH₂)₂Si(CH₃)₂(CH₂)₉SiCl₃,

CF₃COO(CH₂)₁₅SiCl₃,

CF₃(CF₂)₇(CH₂)₂SiCl₃,

CF₃(CF₂)₅(CH₂)₂SiCl₃,

and chlorosilane-based surface active compounds such as;

CF₃CH₂O(CH₂)₁₅Si(CH₃)₂C1,

CF₃(CH₂)₂Si(CH₃)₂C1,

CF₃CH₂O(CH₂)₁₅Si(CH₃)C1₂,

CF₃COO(CH₂)₁₅Si(CH₃)₂C1,

and chlorosilane-based surface active compounds of containing methoxygroup such as;

CF₃CH₂O(CH₂)₁₅Si(OCH₃)₂C1,

CF₃(CH₂)₂Si(OCH₃)₂C1,

 CF₃CH₂O(CH₂)₁₅Si(OCH₃)C1₂, and

CF₃COO(CH₂)₁₅Si(OCH₃)₂C1.

Similar effects could be obtained with such alkoxysilane-based surfaceactive compounds such as CF₃(CF₂)₇(CH₂)₂Si(OCH₃)₃, and CF₃CH₂O(CH₂)₁₅Si(OCH₃)₃ by heating the surface active compound solution.Further, with chlorosilane-based surface active compounds havinghydrocarbon groups such as;

CH₃(CH₂)₉SiCl₃,

CH₃(CH₂)₁₅SiCl₃,

CH₃CH₂O(CH₂)₁₅SiCl₃, and

CH₃(CH₂)₂Si(CH₃)₂(CH₂)₁₅SiCl₃,

can be chemically adsorbed as a monomolecule film. These compounds weresimilarly formed into a monomolecule at room temperature to obtain thehydrophobic and contamination free effects described above.

As has been described in the foregoing, according to the instantinvention a very thin transparent hydrophobic monomolecule film isformed on the transparent glass surface, and therefore the gloss whichis intrinsic to the transparent glass is not spoiled. Further, thehydrophobic monomolecule film is highly hydrophobic and oil-phobic andthus enhances the repellency to contamination characteristics of thesurface. It is therefore possible to provide a highly contaminationfree, high performance transparent glass. Further, an antifogging effectcould be obtained by leaving part of the substrate surface hydrophilic

According to the invention, by using a chemical adsorption method, ahydrophobic monomolecule film with a small thickness (of the nanometerlevel) can be formed on the surface of a transparent substrate withoutspoiling gloss and transparency thereof. If the hydrophobic monomoleculefilm contains a fluorocarbon group, it has excellent hydrophobic andoil-phobic properties and permits improvement of surface contaminationprevention effect. It is also possible to form a chemically adsorbedmonomolecule film having hydrophobic and contamination preventionproperties on one surface and a chemically adsorbed monomolecule filmcontaining hydrophilic groups on the other surface. This treatment thusprovides a transparent substrate having different natures on oppositesides.

It is therefore possible to provide a transparent substrate, which ishighly antifogging, hydrophobic, oil-phobic and contamination free.

While the above invention has been disclosed with respect to specificembodiments thereof, it is not limited thereto. The subjoined claims areintended to be construed to encompass the present invention in its fullspirit and scope including such other variants and modifications as maybe made by those skilled in the art without departing from that truespirit and scope.

What is claimed:
 1. A method of modifying a surface of a moldedtransparent substrate having two surfaces, comprising the steps of: (A)contacting both of the surfaces of the molded transparent substrate witha non-aqueous solution containing a compound having at least twochlorosilyl groups per molecule of compound; (B) washing the transparentsubstrate using a non-aqueous organic solvent capable of removing anyunreacted compound applied in step (A); (C) treating the transparentsubstrate with water after step (B), thereby forming a hydrophilicmonomolecular film composed of a silane material having silanol groups;and (D) treating the transparent substrate having thus formed silanolgroups with a silane-based surface active compound having a reactivesilane group at one end and a hydrophobic group at the other end,thereby laminating a chemically adsorbed hydrophobic monomolecular filmon the hydrophilic monomolecular film.
 2. The method according to claim1, which further comprises, between the steps (C) and (D), the step ofcoating one surface of the transparent substrate with a water-solublecoating film and, after step (D), removing the water soluble coatingfilm, thereby forming a hydrophobic monomolecular film on one surfaceand a hydrophilic monomolecular film on the other surface.
 3. The methodaccording to claim 1, wherein the reactive silane group is achlorosilane group.
 4. The method according to claim 1, wherein thesilane-based surface active compound is represented by the formula:CF₃—(CF₂)_(t)—(R²)r—SiCl_(v)Y_(3-v) where t is an integer of at least 0,preferably 0 to 10, r is 0 or 1, R is an alkylene group of from 1 to 20carbon atoms which may contain a vinylene (—CH═CH—), ethynylene (—C≡—C—)group or may be interrupted by a —O—, —Si(CH₃ )₂— or —COO—, Y is ahydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxylgroup having 1 to 6 carbon atoms and v is an integer ranging from 1 to3.
 5. The method according to claim 1, wherein the material having atleast two chlorosilyl groups is selected from the group consisting of:SiCl₄,SiHCl₃,SiH₂Cl₂, and C1—(SiCl₂O)_(n)SiCl₃ (where n is an integer of1 to 4).